Method of making stereoscopic photographs

ABSTRACT

Improved methods and systems are provided for producing stereoscopic photographs which exhibit optical characteristics resembling those of a hologram in that a photograph is produced by the methods of the invention the aspect of the recorded threedimensional image changes with change of viewpoint about both horizontal and vertical axes. The photograph produced in accordance with the methods of the present invention may be appropriately termed an &#39;&#39;&#39;&#39;integram&#39;&#39;&#39;&#39; or an &#39;&#39;&#39;&#39;integraph,&#39;&#39;&#39;&#39; and it possesses important advantages over the hologram. For example, coherent light, such as laser illumination, is not required for producing or viewing the photograph, the photographic equipment required to produce the photograph is compact and simple to operate, and exposure times for producing the photograph correspond to those which would be required for ordinary twodimensional photography under the same conditions.

I it Dudley j *iiiiired s I m w i 111 3,734,618 May 22,1973

$EARCH Rodi 13; f

i751 Inventor: Leslie Peter Dudley, Los Angeles, 1. Calif.

[73] Assignee: Dudley Optical Laboratories, Inc.,

1, Beverly Hills, Calif.

f1. 32 Filed: Au .24,197o

- 21I 'A l. 196.; 66,356

Related 1.1.8. Application Data {621 Division of Set. No. 747,931,1uly26,1968.

f 52 u.s.c1. .355/132, 95/113? s1 1m.c1 ..G03b 35/00 a 1521 Field ofSearch ..35s/132;9s/1s 1361 References Cited UNITED STATES PATENTS3,072,396 3/1937 Eggert 3,503,315 3/1970 Montebello ..95/l8 P PrimaryExaminer-John M. Horan Attorney-Jessup & Beecher 57 ABSTRACT lmprovedmethods and systems are provided for producing stereoscopic photographswhich exhibit optical characteristics resembling those of a hologram in'that a photograph is produced by the methods of the invention theaspect of the recorded three-dimensional image changes with change ofviewpoint about both horizontal and vertical axes. The photographproduced in accordance with the methods of the present invention may beappropriately termed an "integram" or an integraph," and it possessesimportant advantages over the hologram. For example, coherent light,such as laser illumination, is not required for producing or viewing thephotograph, the photographic equipment required to produce thephotograph is compact and simple to operate, and exposure times forproducing the photograph correspond to those which would be required forordinary twodimensional photography under the same conditions.

2 Claims, 17 Drawing Figures 1 METHOD OF MAKING STEREOSCOPIC PHOTOGRAPHSThe present application is a division of copending application, Ser. No.747,931, which was filed July 26, 1968, in the name of the presentinventor.

BACKGROUND OF THE INVENTION An integram type of photograph consists of alarge number of minute, juxtaposed images produced by an optical screen.The same, or a similar, screen may be used when viewing the photograph.In a preferred form, the screen consists of transparent materialembossed on one surface with an array of small lenticules of sphericalor substantially spherical curvature. The screen is so located withrespect to the photographic film emulsion or other photo-recordingmedium that the photo-recording surface of the film is at the focus ofthe lenticules. A convenient arrangement is for the screen-filmcombination to be manufactured as a composite unit, the lenticules beingformed on the surface of the film base.

In some applications, it is possible to employ, instead of a screenembossed with spherical lenticules, a device which may be regarded asthe optical equivalent of such a screen. One type of opticallyequivalent screen is made from a pair of cylindrically lenticulatedscreens, the lenticulated surfaces of the two screens being in contactwith each other, and the longitudinal axes of the lenticules of onescreen being at rightangles to the longitudinal axes of the lenticulesof the other screen.

' The photograph with which the present invention-is concerned isproduced by an indirect photographic method such as that described andclaimed in the aforesaid copending application, Ser. No. 747,931. Theindirect method uses a screen-film combination to record an integram ofthe image of the scene or subject,

formed by a primary lens, for example, a camera objective lens. Thescreen-film combination is located at the focal plane of the camera towhich slight modifications have been made. Each lenticule then functionsas a minute field lens, reimaging that portion of the image formed bythe primary lens which would otherwise reach the film direct. In thisindirect me hod, the degree of parallax is governed by the diameter ofthe primary lens. No focus adjustment is required for the purpose ofinsuring sharpness, regardless of the distance of the subject, althoughthe distance of the primary lens from the screen-film combination may bevaried if desired. However, such adjustment has no effect on thesharpness of the imagery, but determines which particular transverseplane of the subject will appear to coincide with the film plane of thecompleted integram.

The reimaging (by the lenticular array) process of the copendingapplication results in a tremendous increase in the depth of field whichwould otherwise be provided by the primary lens alone. The exposure maybe varied by the use of a filter or filters, and/or by the adjustment ofthe shutter speed. The use of a primary lens of relatively largediameter is desirable, and a number of suitable camera lenses are notcurrently available on the market. A significant consideration,moreover, is that lenses designed especially for indirect integraphy canbe produced at a cost substantially below that of equivalent lensesdesigned for regular photography. This is because the rcimaging processrenders it unnecessary to incorporate such precise correction for allthe aberrations in the primary lens.

An important feature of the indirect photographic method of thecopending application resides in the relationship which must existbetween the characteristics of the primary lens, the characteristics ofthe lenticules, and the dimensions of a special type of aperture platewhich is used in conjunction with the primary lens, no iris diaphragmbeing employed. The reason for this relationship is that it is necessaryto insure that adjacent images in the integraphic array are preciselyabutting, and not appreciably overlapping or spaced apart.

The aperture plate used in the aforesaid system preferably consists of amask of opaque material, the center portion of which is pierced toprovide a clear aperture, which is quadrilateral or hexagonal in shape,depending upon the shape of the individual lenticules of the lenticulararray. In general, the f-number of the primary lens must be numericallylower than that of the lenticules. Then, by appropriate selection of thesize of the aperture, the condition specified in the preceding paragraphcan be fulfilled.

lntegrams produced by the indirect method described above present apredominance of stereoscopic zones when viewed from a comparativelyshort distance, such as that customarily adopted in normal reading. Atgreater viewing distances, pseudoscopic zones predominate. This state ofaffairs may be reversed, if so desired, by adopting a suitable printingtechnique when making a reproduction from the original photograph, andthen the picture will appear predominantly pseudoscopic when viewed froma short distance and predominantly stereoscopic when viewed from agreater distance.

The present invention is particularly concerned with improved methodsfor making reproductions of photo graphs produced by the systemdescribed by the aforesaid copending application, and to the compositionof the photographs themselves.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagram showing a portionof a spherically lenticulated film placed at the focus of the cameralens, together with a mask having twin apertures;

- FIG. 2A is a diagram, partly in section, showing a portion of aspherically lenticulated film placed at the focus of a camera lensprovided with a square aperture;

FIG. 2B is a diagram corresponding to FIG. 2A, the lens, and aperturebeing viewed on axis;

FIG. 2C is a front view of the lenticular surface, partly broken away,and showing the square peripheries of the lenticules;

FIGS. 3A, 3B and 3C are similar, respectively, to FIGS. 2A, 2B and 2C,except that the lens aperture and the lenticules have hexagonalperipheries;

FIGS. 4A4F relate to characteristic features peculiar to optical imagingprocesses involving the use of spherically lenticulated screens or film;

FIG. 5 is a diagram illustrating the effect of the twofoldimage-inversion resulting from the joint action of the primary lens andthe spherical lenticules;

FIG. 6A is a diagram showing a method of making contact prints;

FIG. 6B shows a lenticular screen laminated to the surface of thecontact print formed by the method of FIG. 6A; and

preciably overlapping or spaced apart; moreover, it is desirable thatthe entire area of the photosensitive surprints, at unit magnification,in the form of transparencies.

" DETA'ILED DESCRIPTION OF THE ILLUSTRATED reimage these two views as alarge number of minute,

' --disc-shaped images. Each such disc, occupying but a .fraction of thearea of emulsion behind the associated lenticule, contains a minuteimage of some small element of the subject. The left-eye" and right-eye"images are interdigitated laterally across the film emulsion as denotedin the diagram by, respective, l and r. Consider the mask M to bepierced with a third small aperture located midway between the aperturesL and R. This, will result in the formation of a third array of littledisc images, interdigitated between those denoted land r. It will beclear that the third view constituted v by this additional array ofimages will represent an aspect of the subject which is rightward withrespect to that dueto the aperture L, and leftward with respect to Ithat due' to the aperture R.

Next, consider the mask M to be pierced with further :small apertures atintervals extending, not only across the horizontal dimension of themask, but also along the vertical dimension (i.e., the dimension normalto the plane of the diagram). Each such aperture will resuit in theinformation of a further array of image elements displaced from theirneighbors by amounts, and in directions, dependent upon the location ofthe aperture in the mask M. Now consider, finally, that the-mask M isentirely rembved, this being equivalent to introducing a suffi- Qcientlylarge number of overlapping apertures. 'fiie image formed behind eachlenticule will now be a small disc-shaped image of an element of thesubject, the aspect of that element which is presented by the disc imagechanging progressively along every axis in the plane of the disc.According to the values chosen for I the optical components of thesystem, matters can be so adjusted that the little disc images areeither spaced apart, just abutting, or overlapping; under any of theseconditions, moire effects will be exhibited by the completed picture.Inorder that such moire effects may be avoided, or at least reduced to alevel at which they are not obtrusive, it is necessary to arrangematters so that adjacent elementary images in the array of which thepicture is composed are precisely abutting, and not apface within thefilm format shall undergo exposure, but not multiple exposure. It willbe evident that it is imposother than square or hexagonal, but departurefrom the preferred shapes introduces problems in the manufacture of thelenticular screen and in other areas without yielding any additionaladvantage to offset these difficulties.

FIGS. 3A, 3B and 3C are diagrams similar to FIGS. 2A, 2B and 2C,respectively, but the apertures and lenticules have hexagonalperipheries. Both sets of diagrams will be considered in more detailsubsequently herein.

The series of six diagrams in FIGS. 4A-4F will facilitate anunderstanding of certain characteristic features peculiar to opticalimaging processes involving the use of spherically lenticulated screensor film.

Consider, first, FIG. 4A, which diagram represents a square object ortarget subdivided into four smaller squares bearing the numerals 1, 2, 3and 4. If imaged by a regular camera lens, the orientation of thenumerals, as viewed from the back of the camera, will be as indicated inFIG. 48. If the image is recorded on a photographic plate or film, aprint can, of course, be made; this print, after rotation through ISO inthe image plane, will display the numerals in the same orientation asthat of the numerals on the target. This print is represented by FIG.4C, which diagram is identical to FIG. 4A.

Now consider FIGS. 4D and 4F, the target being I represented by FIG. 4D.The remaining two diagrams. illustrate the results of imaging the targetby the method described below. Consider four adjacent sphericallenticules, in square array, on a piece of film or a screen used inconjunction with an imaging system of the type shown in FIGS. 2A and 2B.The image formed at the focal plane of an individual lenticule is not animage of the entire scene within the field of the primary (camera) lens;it is an image of some minute portion of that scene, which particularportion being dependent upon the location of the lenticule within thecamera format. Accordingly, it is to be assumed in the present case thatFIG. 4D represents just a very small portion of a much larger target,the portion illustrated being of such dimensions that its imageprecisely fills the area of 5 sible for all these conditions to befulfilled if the ele- Q l EMBODIMENTS mentary images are disc-shaped.Thus, for example, Referring first to FIG. 1, this diagram is intendedfor with disc-shaped images, matters can be so adjusted use inexplanation of certain optical characteristics of that each disc justcontacts the periphery of each of the the indirect stereoscopicphotographic system deadjacent discs. However, such contact is possibleat scribed and claimed in the aforesaid copending applionly certainpoints on the periphery of each disc, thus cation. The diagram shows apiece of spherically lenticleaving a multiplicity of unexposed areas.ulated film F placed at the focus of a camera lens 0. A feature of thesystem described in the copending The lens is assumed to have a largeeffective diameter, application is to provide means for modifying theshape I preferably greater than the normal interocular distance of theelementary images so that the conditions necesi -of about 2 I: inches.An opaque mask M is located sary for obviation or minimization of moireeffects can close to the lens, this mask being pierced with a pair of beachieved. One of the preferred methods involves the small, laterallyspaced circular apertures L and R, the use ofa plate or diaphragm havinga square aperture as 7 separation between the apertures beingapproximately shown schematically in FIGS. 2A and 2B. The effect ofequal to the normal intcrocular distance. As a result of this apertureplate, used in conjunction with lenticules the illustrated arrangement,the small portions of the having square peripheries, is to change theshape of the -.lens which receive light entering through he twoaperelementary images from circular to square, and to prot res functionsimilarly to two separate lenses. Thus, a vide that the sides ofadjacent squares are precisely i left-eye" view of the subject isdirected toward the abutting, and neither overlapping nor spaced apart.It film by one element and a right-eye" view is so diis possible, atleast in theory, to fulfill the required conrected by the other element.The lenticules on the film ditions by the use of elementary imageshaving a shape name...

the total format of the four-lenticule array. Now, in the absence of thelenticules, the image would be oriented as shown in FIG. 48. However,due to the presence of the lenticules, the elementary image within thefon'nat of each individual lenticule undergoes rotation about its centerthrough 180; accordingly, the orientation becomes as shown in FIG. 4E.

in order that the complete picture (of which FIG. 4E,

as previously indicated, represents just a small part), in the form ofeither the original or a print may be viewed the right way up, it isnecessary for the complete picture to be rotated through 180. Thisfurther rotation results, finally, in the orientation represented inFIG. 4F. Thus, the picture as a whole is now the right way up, elementNo. 1 being above element No. 3 and to the left of element No. 2, whileelement No. 4 is below element No. 2. However, each individual elementis now inverted; in consequence of this inversion, the panoramic effectsexhibited by pictures produced by this technique are the opposite ofthose experienced when viewing an actual three-dimensional subject orscene.

Thus, when viewing an actual scene, if the observer moves his head tothe left, a more leftward aspect of the scene is presented to his eyes;if he moves his head to the right, then the view presented to his eyesis more rightward in aspect. Again, when viewing a real-life scene, ifthe observer raises his head, the aspect of the scene presented to hiseyes changes to one appropriate to his more elevated viewpoint.Similarly, if he lowers his head, the aspect changes to one appropriateto his lower viewpoint. However, in the case of a picture pro duced bythe method under discussion, the changes in aspect which result fromchanges in the observer's viewpoint are the opposite of those justindicated. if, for example, the observer moves his head in a lateraldirection, then the aspect of the image presented to his eyes becomesmore rightward if he moves his head to the left, or more leftward if hemoves his head to the right. Similarly, if the observer moves his headin a vertical direction, the aspect changes to one appropriate to alower viewpoint if he raises his head, or to one ap propriate to ahigher viewpoint if he lowers his head.

It is found, in practice, that the anomalous effects referred to aboveare not at all disconcerting to the observer; in fact, they will usuallypass completely unnoticed by him unless his attention is drawn to themby someone who is familiar with the optical characteristics of theprocess. There are, moreover, methods generally involving sequentialprinting or reproduction by which these anomalies can be avoided so thatthe panoramic effects are consistent with those observed in everydayvisual experience. These mthods involve rotation of the individualpicture elements, instead of the array as a whole, through 180' in theimage plane.

It might, perhaps, be thought that inversion of the individual imageelements, as represented in FIG. 4F, would result in impairment of thequality of the picture. However, in general, such is not the case forthe following reason. In most practical cases the image elements are sosmall that the information within the area of a single element isinsufficient for identification as a feature of the picture. Suchidentification is made possible, however, by the eye's ability torecognize the larger amount of information contained within the net areaof several adjacent elements.

FIG. 5 illustrates, in a simplified manner, the effect of the two-foldimage-inversion resulting from the joint action of the primary lens andthe spherical lenticules; that is to say, the diagram shows why acontact print, a reversal positive or a negative produced in accordancewith the methods of the present invention may be seen eitherstereoscopically or pseudoscopically, depending upon the observer'sviewing distance. A piece of spherically lenticulated film is shown inFIG. 5 as being viewed by an observer, first from a position (a), andthen from a more distant position (b). ln each instance the observer'sleft and right eyes, respectively, are denoted by E and E At the focalplane of each lenticule, the numerals l and 2 are used to denote theedges of the elementary image depicting, respectively the extremeleftward and extreme rightward aspects of that image.

Thus, for the picture to be seen in the stereoscopic mode, light raysemanating from points in the elementary images nearer to the edgesdenoted by the numeral 1 should reach the observers left eye; similarly,rays emanating from points nearer to the edges denoted by the numeral 2should reach his right eye. Consideration of the diagram will show that,due to the refractive effect of the lenticules, this condition isfulfilled when the observer is at a location such as that denoted by(a). When, however, he moves to a more distant location, such as thatdenoted by (b), the opposite condition prevails, with the result thatthe picture is seen in the pseudoscopic mode. a Consider that thepicture has been so recorded or reproduced that the little numerals and2 in FlG. 5, respectively, denote the extreme rightward and leftward(instead of vice versa) aspects of the elementary images. This can beaccomplished by means of the transposition process described in theapplicant's copending US. Pat. application, Ser. No. 747,996, entitledlmprovements in integral PHotography. Clearly, the situation will now besuch that the picture is seen pseudoscopically from relatively nearviewpoints, such as (a), and stereoscopically from more distantviewpoints, such as (b).

Reverting to F IG. 2A, L denotes the primary or camera lens, and Fdenotes a piece of spherically lenticulated film on which the subject orscene is recorded. The lens L is provided with an aperture plate A whichmust be located in the plane of one of the lens pupils. In theillustration, the aperture plate is represented as being between thefront and back components of the lens in the position normally occupiedby the iris diaphragm, this being generally the most suitable location.The aperture plate is shown in sectional side elevation in FIG. 2A, andin front (or rear) elevation in FlG. 2B. The aperture itself is square.

The dimension i is the effective focal distance of the lens L from thefilm F; thus, this distance exceeds the focal length of the lens exceptin some special cases (e.g., high altitude aerial photography) in whichthe lens is focused at infinity. In view of the fact that the thicknessof the film is insignificant compared to the distance i, it is of littleconsequence whether the latter dimension be measured from the lens tothe lenticules, to the film emulsion, or to some intermediate plane. Forthe present purpose it is most convenient for the distance i to be, asindicated in the diagram, that from the lens to the plane containing thecenters of curvature of the lenticules.

The symbol f denotes the focal length of the lenticules; i' is thedistance of the summit of each lenticule from the photosensitivesurface; r is the radius of curvature of the lenticules, and w is thewidth of each lendcule or the lenticular pitch distance. In addition,213 denotes the acceptance angle of the lenticules, and 2a is theeffective f-cone angle of the lens L which would be available if theaperture plate A were to be replaced by a regular, circular stop or irisdiaphragm. For the most economic design of the complete system, it ispreferable that this f-cone angle be that corresponding to the maximumaperture at which the lens is designed to operate. The radius of thecircular aperture is denoted by r, and the halflength of a side o thesquare aperture by which the circular aperture is replaced is denoted by.r.

With the circular aperture in position, the imagery formed at the focusof each lenticule would occupy a circular area having a diameter d (seeFIG. 2A) in excess of the pitch distance or lenticule width w. Hence,the recorded picture would be composed ofa multiplicity of littleoverlapping discs, and would consequently exhibit intolerable moireeffects when viewed through the lenticulated surface. If the diameter ofthe circular aperture were to be reduced so that the effective f-cone 25angle of the primary lens is equal to the acceptance angle of thelenticules, then:

a B and d w Under these conditions, the picture would still be composedof a multiplicity of elementary disc-shaped images, but the peripheriesof adjacent discs would then be just in contact, and neither appreciablyoverlapping this condition would be made even worse, the image discsbecoming smaller and the star-shaped areas be coming larger.

The solution of the above problem constitutes an important feature ofthe invention described and claimed in the aforesaid copendingapplication, and FIGS. 2A and 2B are to be regarded as representative ofthe means by which the desired end can be attained. It is to be imaginedthat the lenticules on the film F have square peripheries, each boundingan area W X w, their shape thus matching, to a reduced scale, that ofthe square aperture in the plate A. Accordingly, the exposed area at thefocus of each lenticule will be squareshaped instead of disc-shaped; itis required that the dimensions of each of these elementary areas shallbe substantially equal to w X w.

Consideration of the diagram shows that this condition will be met ifthe pencil of rays incident on the lenticule l is appropriatelyrestricted; thus, instead of the pencil containing all the rays withinthe effective fcone, the vertex angle of which is 2 a and the baseradius of which is r, it must contain only those rays within the pyramidthe opposite faces of which include the lenticule acceptance angle 2 B,and which has a square base with sides having a half-length .t. In orderto achieve the most economic design for the system, the value of rshould be the minimum that permits this to be accomplished. The modifiedpencil will then contain those rays comprising the inscribed pyramid ofthe fcone. FIGS. 2A and 2B depict this ideal situation. The

mathematical relationships are:

effective f-cone angle, 2 c: 2 tan r/i acceptance angle of lenticules, 2B 2 tan s/i and radius of lens aperture, r 2 1.4142 .r

10 The last of these three expressions is derived from the dent onlyupon that of the primary lens; this angular field is unaffected by theuse of a specially (e.g., square) shaped aperture in place of the moreusual iris diaphragm, or by the use of spherically lenticulated film inplace of regular, non-lenticulated film. Thus, the acceptance angle ofthe lenticules determines the an gular width of the zones throughoutwhich the completed picture can be viewed stereoscopically, while thefield angle of the primary lens determines the angular field subtendedby the scene recorded.

It is important to note that the use of aperture plate A in conjunctionwith the lens L does not in any way restrict or reduce the area of thelenticulated surface upon which light is incident; even ifthe size ofthe aperture were to be reduced to that ofa pinhole, light from thatpinhole would still reach every part of the surface of every lenticule.In the case of any lens, there is only one perfect" or ideal" f-cone,that is, the f-cone the vertex of which lies on the optical axis.However, the image at the focal plane is formed by light raysconstituting an indefinitely large number of oblique cones,

the vertex angle of each such cone being a little less than that of thef-cone by an amount dependent upon the distance of its vertex from theoptical axis. Similarly, with the aperture plate A in FIGS. 2A and 2B inuse, there is only one perfect f-pyramid," this being the inscribedpyramid of the perfect f-cone. Consequently, this f-pyramid is the onlyone the opposite faces of which subtend an angle precisely equal to thatdenoted in the drawing by 2 B and which illumines the central region ofthe lenticule I. The entire surface of the lenticule is, however,illumined by light rays constituting other, almost identical pyramids.

Thus, for example, the rays p, and p,, also incident on that lenticule,include an angle almost exactly equal to 2 B. Similarly, the angleincluded between the rays p and p, is, again, almost exactly equal to 2[3. Owing to the refractive action of the lenticule, the pyramid oflight defined by the outer pair of rays p, and p, converges to attainminimum cross-sectional dimensions at the plane containing the center ofcurvature. Therefore, if the film were to be sectioned transversely atthis plane, a minute square of light would be seen, the width of thesquare being equal, to a close approximation, to one-third the width ofthe lenticule. From this plane the rays diverge, coming to a focus atthe emulsion surface, forming thereon a square image the width of whichis equal to the width of the lenticule.

In designing a photographic system of the type under discussion, it isgenerally sufficient to base calculations only on the perfect f-cone andthe inscribed pyramid. It is very important, nevertheless, to be awareof the existence of the multiplicity of oblique pyramids of rays whichillumine the entire surface of the lenticular array; disregard of theserays has led, in the past, to misconceptions concerning theconfigurations of the lenticules which can be employed. Thus, the use ofspherical lenticules having circular peripheries, as has been proposedin the past, is entirely unacceptacle.

FlGS. 3A, 3B and 3C, as mentioned earlier, are similar to FIGS. 2A, 2Band 2C, but show the use of lenticules with hexagonal peripheries inconjunction with an aperture plate having the necessary, correspondinghexgonal aperture. With the hexagonal aperture, the relationship betweenr and s is the same as in the case of a square aperture, that is to say,we must have r 2 1.4142 s; this follows from the fact that the aperturein FIGS. 3A and 38 represents the inscribed hexagon of the squareaperture in FIGS. 2A and 28.

FIG. 6A shows schematically a method of making contact prints inaccordance with the teaching of the invention, of either the transparentor opaque type, from pictures recorded by the means depicted in FIGS. 2Aor 3A. For the purpose of explanation, it will be assumed that theoptical arrangement used for recording the pictures is that shown inFIG. 2A. As shown in FIG. 6A, a source of illumination 1 located behinda diffusing screen S is used to fill the field of the lens L with evenlydiffused light. The lens L is the same as, or equivalent to, the lens inFIG. 2A. As in the case of the lens in the earlier diagram, the lens Lis provided with an aperture plate or diaphragm having a squareaperture; the dimensions of this aperture are so correlated with theother parameters of the optical system that each spherical lenticule onthe film F forms a minute, square image of the aperture on the filmemulsion. Thus, the film emulsion is illumined by an array of squarepatches of light, adjacent patches being closely abutting, and neitherappreciably overlapping nor spaced apart.

lt is to be imagined that the film emulsion carries a picture, dulyprocessed, recorded by the method shown in FIG. 2A, and that thethickness and (or) other characteristics of the film are such that thematerial has undergone no perceptible distortion during processing. Thesheet or strip of photosensitive material on which the print orreproduction is being made is shown at P in H0. 6A. If this reproductionis to be in the form of a transparency, the film or other photosensitivematerial used should, as in the case of the film F, possess suchcharacteristics that it does not undergo perceptible distortion as aresult of processing. If the reproduction is to be in the form of anopaque print, such distortion can be obviated very conveniently byusing, for the material at P, emulsion-coated metal (e.g., aluminum)foil instead of the more usual emulsion-coated paper.

As will be noted from FlG. 6A, the material at P is not lenticulated,the emulsion surface being in direct contact with the emulsion surfaceof the film at F. After the exposure has been made and processing hasbeen completed, a lenticular screen L (see FIG. 6B) is laminated to theemulsion surface of the print P.

In general, the optical characteristics of the screen 1. are the same asthose of the lenticular film F. However, this is not an essentialrequirement; the essential re quirement is that the pitch distancebetween the lenticules (about all axes) on the screen L' shall be thesame as the pitch distance between the lenticules on the film F.Provided that this condition is fulfilled and that the screen iscorrectly aligned with respect to the print, no undesirable moireeffects will result.

Insofar as the other characteristics of the lenticular arrays areconcerned, it is permissible, and sometimes desirable, for the opticalproperties of the lenticules on the screen to differ from those on thefilm. For example, by increasing the acceptance angle of the lenticuleson the screen compared to that of the lenticules on the film, theangular width of the viewing zones throughout which the print can beseen stereoscopically is increased, although, at the same time, themagnitude of the stereoscopic effect is reduced. Conversely, by reducingthe acceptance angle of the lenticules on the screen compared to that ofthe lenticules on the film, the angular width of the stereoscopicviewing zones is reduced while the magnitude of the stereoscopic effectis increased.

Use of the lens L and square aperture, as described above, is notabsolutely necessary, as prints can be made with the air of othermethods of illurr ination. The above described method, however, tends toproduce prints of higher quality by minimizing undesirable scatteringand diffusion of light within the film base which would otherwise becaused by the lenticulated nature of the surface through which theprinting light must enter the film.

FIG. 7 is a schematic diagram showing a method of making prints, at 1:1or unit magnification, in the form of transparencies, sphericallylenticulated film being used for both the input material 1' and outputmaterial 0. The general arrangement of the printer shown in FIG. 7 isthat of a known type of symmetrical telecentric system. However, inorder to adapt the arrangement for use in connection with the presentinvention, the mask or aperture plate m which is customarily insertedbetween the two halves of the system must be of a special nature. Thatis to say, the shape and size of the aperture should be appropriatelycorrelated with the optical arrangement used for recording the inputimagery. Thus, for example, if the input imagery is recorded by themethod shown in FIG. 2A, the camera lens being provided with a diaphragmhaving a square aperture, then the mask m in FIG. 7 should likewise beprovided with a square aperture of such dimensions that each of theelementary images of that aperture formed on the emulsions of the filmsi and a occupies an area corresponding to the format of a singlelenticule. lt is preferable, for obvious reasons, for the size of theaperture in the mask m to be adjustable.

Although particular embodiments of the methods and systems of thepresent invention are discussed above, it is apparent that modificationsmay be made. It is intended to cover all modifications which fall withinthe scope of the invention in the following claims.

What is claimed is:

l. A method of making copies on the emulsion surface of a photographicmaterial from photographs of a type comprising a transparent supporthaving a number of small, similarly shaped, juxtaposed pictorialelements oriented in a space-filling array on said support, attainmentof said space-filling orientation being accomplished by providing saidpictorial elements with a square or hexagonal peripheral shape such thatthere are no significant spaces between adjacent elements and there isno significant overlapping of adjacent elements, and by providing alenticular screen comprising an array of lenticules having substantiallyspherical curvature and having a square or hexagonal peripheral shapecorresponding with that of the pictorial elements, the orientation ofthe screen lenticules also corresponding with that of the pictorialelements, and there being no significant spaces between the peripheriesof adjacent screen lenticules; said method comprising the followingsteps:

placing the emulsion surface of the transparent sup? port of theoriginal transparent photograph in contactwith the emulsion surface ofthe photographic plate used in recording the original photograph.

# i i t

1. A method of making copies on the emulsion surface of a photographicmaterial from photographs of a type comprising a transparent supporthaving a number of small, similarly shaped, juxtaposed pictorialelements oriented in a space-filling array on said support, attainmentof said space-filling orientation being accomplished by providing saidpictorial elements with a square or hexagonal peripheral shape such thatthere are no significant spaces between adjacent elements and there isno significant overlapping of adjacent elements, and by providing alenticular screen comprising an array of lenticules having substantiallyspherical curvature and having a square or hexagonal peripheral shapecorresponding with that of the pictorial elements, the orientation ofthe screen lenticules also corresponding with that of the pictorialelements, and there being no significant spaces between the peripheriesof adjacent screen lenticules; said method comprising the followingsteps: placing the emulsion surface of the transparent support of theoriginal transparent photograph in contact with the emulsion surface ofthe photographic material on which the copy is to be made; admittingprinting light through the spherically lenticulated surface of theaforesaid transparent photograph; processing a resulting copyphotograph; and applying the spherically lenticulated screen to theemulsion surface of the resulting copy photograph.
 2. The method setforth in claim 1, in which the printing light is transmitted to thelenticulated surface of the original transparent photograph by way of anoptical system comprising a lens and aperture plate having the sameoptical characteristics as the lens and aperture plate used in recordingthe original photograph.